Abstract Our health care system is fragmented, which leads to suboptimal outcomes for high-risk populations with chronic conditions, such as cardiopulmonary disease, combined with complex medical or social needs. Bundled payments are an alternative payment model (APM) that incents efficiency by holding providers accountable for costs and quality across an entire episode of care. The Center for Medicare and Medicaid Innovation (CMMI) launched the Bundled Payments for Care Improvement (BPCI) initiative in 2013; a new version of this program, BPCI-Advanced (BPCI-A), replaces BPCI in October 2018. Under both, participants that meet cost targets keep the savings, while those that fail to do so pay Medicare back the difference. BPCI- A has increased the financial incentives and added quality measures to further incentivize improvements. Bundled payments provide strong incentives for providers to better-coordinate services and redesign care, which could be very helpful for medically or socially high-risk older adults. These are populations for which clinical innovations are sorely needed, and knowing which ones are being tried and appear to be working could be very helpful in improving quality of care. On the other hand, bundled payments could induce providers to avoid those patients or skimp on care, which could result in poor outcomes. Our overarching hypothesis is that the financial incentives in BPCI had adverse consequences in high-risk cardiopulmonary patients, while the enhanced incentives and use of quality measures in BPCI-A will reduce some of those consequences. Quantifying the impact of BPCI-A on high-risk populations is critically important as Medicare and other payers increasingly shift towards these and other alternative payment models. Examining a variety of medical and surgical cardiopulmonary conditions that represent a range of acuity and complexity, our aims are to 1) Using claims data, determine how BPCI and BPCI-A impact cardiopulmonary spending, access, and outcomes for medically and socially high-risk populations; 2) Using a national survey, identify predictors of participation in BPCI-A, and key approaches to care redesign; and 3) Combining claims and survey data, determine patient, hospital, market, and strategic predictors of success under BPCI-A. Our proposed work will provide timely information to inform annual updates to BPCI-A, and identify clinical interventions that are strong candidates to improve cardiopulmonary care for all patients. Such work could help to protect and optimize outcomes among high-risk populations. Absent these findings and the resulting policy recommendations, BPCI-A could have unintended adverse consequences.